Device for indentifying coins

ABSTRACT

A device for electronically identifying coins, or the like, is described in which coins fed along a feed path are illuminated by light passed from a light source essentially perpendicularly to the feed path. A photosensitive sensor receives the light which passes the coin and converts it to an electric signal representative of the coin diameter. The device utilizes a column-like light source and a lens assembly intermediate the coin and the sensor whereby the size requirements of the sensor are reduced.

BACKGROUND OF THE INVENTION

This invention relates to a device for identifying coin type articles,encompassing all of the coin types known to those of ordinary skill inthe art on the basis of the diameter thereof, comprising

a coin path for feeding coins;

a light source for illuminating the coin on the path in a directionessentially perpendicular to the plane of the path; and

a photosensitive sensor for converting the light which passes the coininto an electric signal dependent on the diameter of the coin, or thelike.

In coin identification devices of the above type, the light receiversare formed, either by optic fibres the ends of which are arranged atsuitable heights in accordance with the diameters of the different cointypes, or by columns consisting of photodiodes or some otherphotosensitive elements. These kinds of devices for determining thediameter of a coin, are known e.g. from British Patent Applications 2115 547 and 2 176 038 and British Patent specifications 1 379 473 andU.S. Pat. No. 4,249,648. The use of a sensor according to British PatentApplication 2 176 038 requires that the coin be in contact with the pathwhen it passes the sensor. On the other hand, this kind of sensorarrangement merely enables the different coin types to be separated fromeach other, whereas foreign coins, for instance, which fall betweenthese coin types are included in the group of the next smallest cointype, and it is not possible to exclude them from the counting. Further,when this kind of device is modified so as to be operative with anothercountry's coins, a new basic adjustment is required, i.e. the fibreshave to be arranged at suitable heights through experimentation. Thedevices disclosed in British Patent Application 2 115 547 and BritishPatent Specifications 1 379 473 and U.S. Pat. No. 4,249,648 utilizephotodiode rows, by means of which the size of a coin or some otherobject can be determined on the basis of the number of photodiodesshadowed by the coin. The sorting accuracy of devices of the above typecould possibly be improved by increasing the number of the fibres orphotodiodes, whereby, in theory, it would be possible to determine thediameter very accurately. In practice, however, the formation of ameasuring sensor consisting of a great number of fibre ends orphotodiodes is difficult and, in any case, causes considerable costs onaccount of the complicated structure as well as requiring the detectorto be attached to each fibre or photodiode.

Swedish Patent Specification 397 420, in turn, discloses apparatuscapable of identification of coins, or the like, on the basis of thearea thereof. In a device according to this publication the lightreceiver consists of a large-area sensor formed by four solar cells, bymeans of which sensor the area of the coin can be determined on thebasis of the total amount of light gone passing the measuring point atthe measuring moment. For obtaining a correct measuring result, theremust not be more than one coin at a time within the measuring area,which, retards considerably the operation of the device. Moreover such adevice has to be provided with means for preventing more than one coinentering the measuring area. In addition, the calibration of theresponses of the different parts of the large-area sensor in suchdevices is also difficult, if not impossible.

SUMMARY OF THE INVENTION

The object of the present invention is to provide meter of coins with anaccuracy such that coins having a different diameter can be removed fromthe coin path. More precisely, the object of the invention is to providea measuring device sufficiently accurate, in view of coin manufacturingtolerances and other factors affecting the coin diameter that it enablesan accurate determination of the diameter of coins. A further object isto solve the problems which have occurred in connection with prioroptically operating devices for the determination of coin diameters anddevices derived therefrom in view of the costs, reliability, andcomplicated structure.

The above objects are achieved by means of a device according to theinvention, which is characterized in that the light source iscolumn-like; that a lens assembly is arranged in front of aphotosensitive sensor, behind the coin path, for projecting an image ofthe light source onto the sensor; and that the sensor is effective tomeasure the amount of light by converting the light in the light emittedcolumn by the light source and passing the coin into an electric signalwhose value is dependant upon the diameter of the coin. Thus thediameter of the coin, is determined as the difference between themeasured signal value of the sensed light amount of an empty path andthe minimum signal value produced by the light measured during thepassage of a coin. When this kind of measuring principle is used, thecoins need not be in contact with the coin path, as the measurement isbased only on the amount of light which is able to pass the coins whenthey traverse the measuring point.

By disposing a lens assembly in front of the sensor, to measure theamount of light and for projecting the image of the light source ontothe sensor, the sensor may be smaller than the light source and, thus,more advantageous in cost. Furthermore, the lens assembly in the presentorganization is able to protect the sensor against dust, which featureis significant as dust formation is a major problem with optic fibres.

In the device according to the invention, variations in the luminosityof the light source due to aging or voltage variation, for instance, arecompensated by the column-like light source that comprises twosuperposed column elements which are equal in size and in which thelight amount emitted therefrom of which is separately adjustable for thecalibration of the readings given by the sensor measuring the totalamount of light. Thus, it is always possible to standardize themeasuring situation irrespective of possible variations in thesensitivity of the sensor or due to dust accumulation on the lensassembly.

DESCRIPTION OF THE DRAWINGS

In the following the device according to the invention and its operatingprinciple will be described in more detail with reference to theattached drawing, in which the single FIGURE depicts a schematicillustration of the device according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The drawing FIGURE shows generally the structure of the device accordingto the invention in which the measuring arrangement thereof comprises acoin path 2 on which a coin 1 is shown; a light source 3 positioned onone side of the coin; and a lens assembly 5 and a photosensitive sensor4 opposite to the light source and behind the coin. As the column-likelight source 3 is positioned in an upright position in front of the coinpath 2 and an image of the light source is projected through avertically elongated slit in the housing containing the light source orin the wall of the member defining the coin path and the lens assembly 5to the sensor 4 measuring the total amount of light on the other side ofthe coin path, the light source is covered by the corn when it passesalong the path in an amount corresponding, in a maximum case, to thediameter of the coin, and the difference between the maximum and minimumamount of light corresponds to the diameter of the coin. That portion ofthe light column which is covered by the coin is independent of thevertical position of the coin on the path, so the coin need not be incontact with the path 2 at the measuring moment. The coin 1 isilluminated in a direction essentially perpendicular to the plane of thecoin path, i.e. the plane of the coin 1. The function of the coin path 2is to feed the coins to the measuring means essentially in the desiredplane and separately from each other. Thus, the coins need not be passedone by one on to the path, which would result in too low a countingrate. In the device according to the invention it is necessary to insurethat the coins are not positioned side by side on the path, but thisrequirement relatively easy to effect mechanically, whereby collisionsalong the path can be regarded to belong to the normal operation of thedevice. Even when such collisions result in a coin being moved off thesurface of the path at the measuring point, the measuring accuracy isnot affected due to the operating principle of the device according tothe invention.

The use of the lens assembly 5 enables the light column 3 to beprojected to the photosensitive sensor 4 in a smaller size, whereby thesensor may be e.g. a PIN diode. A signal proportional to the totalamount of light from the light column 3 is converted into an electricsignal and passed from the photosensitive sensor to an A/D converter 6for converting the measuring value to a digital value. The converter 6may be e.g. an 8-bit A/D converter. From the converter 6 the digitalmeasuring values are transferred to a processor 7 which carries out thecalculations with the measuring values and calibrates the measuringarrangement. When the amount of light at the sensor 4 exceeds apredetermined level for a certain period of time, the processor 7detects that the path 2 is free and compares the voltage level of thesensor 4 to a level set at the manufacturing stage of the device andcorrects a current generator 8 of the light source 3 in a correspondingway. The correction to be carried out at one time is so small that thesawing or hunting effect caused by the adjustment does not cause anerror in the end result but it merges into the disturbances and noiseoccurring in the system in any case. Thus, the correction can be made inparallel with the normal calculation process and, in practice,correction is carried out continuously between measurement of the coins,being interrupted only for the time of the proper measuring.

The column-like light source 3 comprises two separate column elements,such as two LED columns 3a and 3b. It is also possible that, due tomanufacturing inaccuracies, different amounts of light are obtained fromthe different LED columns with the same current, and the amount of lightdoes not necessarily change in the same way with the ageing of the LEDs.Even though the columns could be made equally luminous at themanufacturing stage of the device, the situation does not necessarilyremain unchanged when the device ages.

Since the junction point of the LED columns 3a and 3b is positioned inthe middle of the centre of the lens assembly 5, the images formed atthe photosensitive sensor 4 by both the columns are equally large. Alsothe light amount of the LED columns 3a and 3b can be adjusted to thesame value simply by selectively extinguishing the light emitted fromthe columns respective and by defining the different between the setvalues of the columns, the difference being then maintained duringnormal measuring. This kind of balancing of the light amounts of the LEDcolumns is preferably carried out each time the current to the device isswitched on. After the balancing, the light amount of the bottom, i.e.the empty path is set to a certain predetermined value, which is againcarried out by means of the current generator 8. In this way onecalibration point of the measuring device can be calibrated. The othercalibration point is obtained by thereafter extinguishing the lowercolumn, so that an artificial measuring situation is obtained whichcorresponds to a coin 1 passing along the coin path 2 and having adiameter equalling in size with the lower LED column 3b, and bycomparing the light amount thus obtained to a value stored in thepermanent memory at the calibration stage of the device. If thiscomparison reveals an essential difference between these values, theoperation of the device is faulty. In this way the device, itself, isable to detect even a relatively small malfunction of the measuringsystem.

The processor 7 carries out the calculation of a numerical valuerepresenting the diameter of the coin, or the like. When the amount oflight from the sensor 4 falls below a predetermined level, the processor7 starts to form a moving average from the last 16 samples,simultaneously storing samples in the memory for later examination. Themoving average is determined in two parts, the first part being formedby the first eight samples and the second part by the last eight samplesin this group of sixteen samples When the average value of the group ofthe first eight samples becomes smaller than the average value of thegroup of the last eight samples, the amount of light has reached aminimum value thereof and starts to grow again. The last sample of thegroup of the first eight samples is thus nearest to the maximum diameterof the coin, or the like. In order to improve the sorting accuracy ofthe measuring arrangement, the sum of a number of samples, in practice30 to 40 samples, taken before the sample representing the maximumdiameter, which sample is included, is calculated and the sum soobtained is divided by a figure depending on the number of the samples.In this way it is possible to eliminate the dependence of the obtainedvalue on the path velocity of the coins. In practice, a sortingcapability of 0.05 mm is obtained when an 8-bit A/D converter 6 is used.This can be regarded as fully sufficient, taking into consideration themanufacturing tolerances of the coins and the diameter variationsoccurring therein in use. The sampling interval, for example, may bee.g. 200 microseconds. Thereby the moving average is determined for atime of 3.2 milliseconds. Accordingly, the point representing themaximum diameter of the coin is available 1.6 milliseconds after themiddle point of the coin has gone past the measuring point. When thetime required for the treating of the values in the processor, e.g. 4.4milliseconds, is added thereto, the device is capable of determining thediameter of the coin six milliseconds after the middle point of the coinhas gone past the sensor 4. Since the number of the samples obtainedfrom each coin also depends on the path velocity of the coin, the momentwhen the coin is positioned by a sorting/rejecting unit 10 on the pathcan be determined by means of the path velocity. Thus, a coin can beremoved reliably from the path if it is detected that its diameterdeviates from that of the coins for which the device has been calibratedSo it is easy to remove foreign coins from the counting process. Thesorting/rejecting unit 10 is controlled by a central processor 9 whichreceives information from the processor 7 on the diameters andvelocities of the coins detected on the path. The central processor 9then either sorts out the coin to an acceptable coin type on the basisof the diameter data and adds the monetary value of this coin to the sumshown on a display 11, or controls the sorting/rejecting unit 10 so asto remove from the path 2 a coin which does not belong to any one of theacceptable coin types.

Since the operation of the device according to the invention is based onthe measurement of the amount of light and, on the other hand, ontypical measuring values determined for each coin type by means of thiskind of measurements, there is no problem in modifying the counter sothat it suits species of coins of different countries. When the,.monetary values of the coins of a new country are input to the device,the number of the coins and the corresponding values are firstprogrammed in the device, whereafter a calibration run is carried out,in which a certain number of each coin type is passed through thedevice. The device forms coin groups, the average value of which iscalculated and the upper and lower acceptable limits are determined foreach type by giving the mechanical tolerances of the coins of thecountry in question.

The device according to the invention has been described above only onthe basis of one specific embodiment, and it is to be understand that itis possible to modify the structure of the device as well as the ways ofcalculating the measuring values dependent on the coin diameter withoutdeviating from the scope of protection defined in the attached claims.Since the device according to the present invention is based on theidentification of coins, or the like, exclusively on the basis of thediameter thereof, it is obvious that it does not give fully reliableinformation on whether all the coins fed into the device are genuine.This information can be ascertained by additional units provided infront of or behind the device, the operation of which devices may bebased on the determination of the thickness, for instance, or on thedetermination of the material of the coin by means of an inductivemethod. Accordingly, by combining the device according to the inventionto units previously known from coin sorting a device can be obtainedwhich both identifies the genuineness of the coins and calculates thevalue thereof extremely reliably.

We claim:
 1. A device for the identification of coins on the basis ofthe diameter of the coins, comprising:a coin path (2) for feeding coins(1); a column-like light source (3) comprising two superposed columknelements (3a3b), equal in size, for illumianting a coin (1) on the coinpath (2) in a direction essentially perpendicular to the plane of thecoin path (2); a photosensitive sensors (4) that measures the amount oflight sent by the column-like light source (3) that passes the coin (1)to convert this light into an electric signal dependent on the diameterof the coin; and a lens assembly (5) arranged in front of thephotosensitive sensor (4) and behind the coin path (2) for projecting animage of the light from the column-like light source (3) that passes acoin (1) onto the photosensitive sensor (4);wherein the amounts of lightfrom the column elements (3a, 3b) of the column-like light source (3)are separately adjustable to permit calibration of the readings given bythe photosensitive sensor (4) measuring the amount of light.